GI Physiology Flashcards
Which receptors are involved in swallowing?
Trigeminal and facial nerves, glossopharyngeal receptor, hypoglossal and vagus nerves
What is dysphagia and which patients are likely to suffer from this?
Difficulty swallowing, stroke patients.
What is the oesophageal hiatus?
The point at which the oesophagus passes through the diaphragm
What causes a hiatus hernia?
Acid reflux causes stomach to protrude up through diaphragm
What is the name of the healthy cells that line the oesophagus?
Squamous cells
What seals the stomach and prevents acid and enzymes entering the oesophagus?
The lower oesophageal sphincter/ cardiac sphincter
What is Barrett’s oesophagus?
Erosion of the squamous cells due to stomach contents moving up into oesophagus. Squamous cells are replaced with pre cancerous specialised columnar cells
What is the purpose of mucin?
It is a glycoproteins secreted by the salivary glands to lubricate for swallowing
What is the function of G cells?
Secrete the hormone gastrin which stimulates acid production
What is the function of chief cells?
Secrete pepsinogen and lipase
What is the function of parietal cells?
Produce HCL to cleave pepsinogen into pepsin (a protease). This is a positive feedback mechanism because pepsinogen is a protein so cleaned by pepsin to secrete even more pepsin
What prevents the stomach from digesting itself?
Right junction structures restrict movement of acid/protease between cells and down to the underlying tissues. Mucous is alkaline so neutralises HCL and forms physical barrier between HCL and stomach. Pepsin released in inactive form (pepsinogen)
Why is helicobacter pylori a problem?
It infects gastric mucosa, decreasing barrier efficacy which can cause an ulcer
Describe peristalsis
Circular muscles contract to prevent backwards movement of food bolus up GIT, longitudinal muscles then contract to push contents further along GIT
List the adaptations of the small intestine that make it suitable for absorption
Folds called plicae are lined with villi and microvilli to create a large surface area. Epithelium layer is only one cell thick so has a short diffusion pathway. Enzymes convert non-absorbable macromolecules into small, absorbable molecules
